Heat exchanger

Abstract: The invention relates to a heat exchanger (1) provided with a feed opening (2) and a discharge opening (3) for a medium, which openings are mutually connected by a duct (4) substantially rectangular in cross section, through which duct transverse ducts (5) for a medium on the outside of the insert heat exchanger are arranged practically perpendicularly of the flow direction of the medium in the duct.

Description: The invention relates to a insert heat exchanger. In the transfer of heat from a first medium to a second medium the efficiency of the transfer is of very great importance. Another important factor is the complexity of the construction of the heat exchanger. This is of particular relevance in the manufacture thereof and in the later servicing of the heat exchanger. The European patent application EP-A-0 291 322 discloses a heat exchanger according to the preamble of claim 1, especially a heat exchanger in the form of a comfort heat exchanger. The heat exchanger comprises two manifold elements adapted to receive and discharge fluid, and a plurality of tube units transverely located between the manifolds. The manifolds are held in spaced apart relationship by end panels thus forming a duct substantially rectangular in cross section. By feeding water through the tube units an air flow between the manifolds and the end panels can be heated or cooled as required in the heating and airconditioning systems of automobiles. The present invention has for its object to provide a structurally simple insert heat exchanger which is comparatively inexpensive to manufacture and which moreover produces a very high efficiency. The invention has the additional objective of combining a high insert heat exchanger efficiency with a limited volume of the heat exchanger. This is achieved by the invention with a insert heat exchanger in accordance with claim 1. Such a insert heat exchanger combines a relatively high efficiency with a very simple and therefor inexpensive construction. The United States patent US-A-4 034 803 discloses a tubular air preheater for transfer of heat from hot flue gasses. The air preheater comprises a feed opening and a discharge opening for clean air for combustion purposes, which openings are mutually connected by a duct substantially rectangular in cross section. Inside the rectangular conduit are a plurality of heat exchange elements containing a plurality of thin walled tubes in which flue gasses flow in counter flow relative to the cool air flow for combustion purposes through the rectangular conduit. Cross sections through the transverse ducts are in preference practically circular. The heat exchanger is found in this case to produce a high efficiency. The largest surface area of a cross section through a transverse duct perpendicular to the flow direction of the medium through the duct preferably amounts to about 40% of the surface area of the cross section through the duct. This ratio is found to produce an exceptionally favorable result. The form of the duct is in preference substantially U-shaped. This shape enables a very compact construction of the insert heat exchanger. The insert heat exchanger is preferably provided with a combustion chamber. In this case the heat exchanger is used as an element for producing as well as generating heat. The combustion chamber preferably has a substantially circular cross section and preferably connects onto an outlet duct for combustion gases as according to the already described heat exchanger. The substantially circular cross section of the combustion chamber has the advantage that the minimum distance from the wall of the combustion chamber to the burner, which will generally have a round shape, is maximal. If the combustion chambers connects onto the outlet duct for combustion gases no heat will be lost when combustion gases are transported from the combustion chamber to the outlet duct. It is further possible with such a heating element to place the whole device in a medium for heating. The heat exchanger with combustion chamber is preferably arranged in a boiler which is connected to a solar collector. Particularly in this situation there will be a limited temperature difference between the heating waste gases and the already pre-heated medium for heating, so that particularly in this case a heat exchanger with a high efficiency is desired. A plate is preferably arranged at a small distance beneath the heat exchanger for generating a desired flow pattern of the second medium on the outside of the heat exchanger. The plate will be able to influence the natural convection pattern of the medium on the outside of the heat exchanger such that a strong upward flow through the transverse ducts of the heat exchanger will occur, thereby enabling an especially good heat transfer. The present invention will be elucidate with reference to the non-limitative embodiment of a heat exchanger according to the present invention. The figure shows a partly cut away perspective view of a insert heat exchanger according to the invention, inserted in a vessel and provided with a combustion chamber. An insert heat exchanger 6, which is placed in a vessel 7, is provided with a feed opening 8 for fuel and oxygen-containing combustion gases. These gases are fed to a burner 10 situated in a combustion chamber 9. The latter has a practically circular cross section to prevent the minimum distance between the wall of the combustion chamber 9 and the, in this case, round burner 10 being very small at a particular position. The combustion chamber 9 is connected to a rectangular outlet duct 11 for combustion gases. The rectangular duct 11 can be manufactured from sheet metal material such as aluminium or stainless steel but also from steel of a lesser quality, and subsequently provided with a coating layer. Conceivable here for instance is a coat of enamel. The transition from the combustion chamber 9 to the rectangular outlet duct 11 is a smooth one and can for instance be manufactured by forging a rectangular duct to a round shape at the position where the combustion chamber 9 is formed. The rectangular outlet duct 11 for combustion gases forms here the heat exchanger for generating the heat created by the combustion in the combustion chamber 9 to the medium in the vessel 7. The rectangular outlet duct 11 is provided for this purpose wiht transverse ducts 12 placed perpendicularly of the flow direction of the combustion gases in the rectangular duct 11. The transverse ducts 12 shown in this figure all lie in the same direction. This does not however always have to be the case. The cross section through the transverse ducts 5 are practically circular, although this does not necessarily have to be the case either. They may for instance have another cross section. A possibility here is for instance a rectangular cross section. Through natural convection of the medium in vessel 7 a flow 13 will occur wherein the medium for heating will flow through the transverse ducts. The rectangular outlet duct 1 has substantially a U-shape and the discharge opening 14, where the cooled waste gases will leave the insert heat exchanger 6, is joined like the feed openings to a flange 15. This flange 15 enables simple placing and removal of the insert heat exchanger element 6 into and out of the vessel 7. The insert heat exchanger 6 described in this figure can be applied to particularly exceptional advantage in a solar boiler.

Claims: Insert heat exchanger (6) provided with a feed opening (8) and a discharge opening (14) for a first medium, which openings (8; 14) are mutually connected by a duct (11) substantially rectangular in cross section, through which duct (11) transverse ducts (12) for a second medium on the outside of the insert heat exchanger are arranged practically perpendicularly of the flow direction of the first medium through the inside of the duct (11), characterized in that the feed opening (8) and the discharge opening (14) are both provided with a flange or both placed in a common flange (15) enabling in use placing and removal of the insert heat exchanger (6) into and out of a vessel (7). Insert heat exchanger (6) as claimed in claim 1, characterized in that cross sections through the transverse ducts (12) are practically circular. Insert heat exchanger (6) as claimed in claim 1 or 2, characterizedi in that the largest surface area of a cross section through a transverse duct (12) perpendicular to the flow direction of the medium through the duct (11) amounts to about 40% of the surface area of the cross section through the duct (11). Insert heat exchanger (6) as claimed in any of the claims 1-3, characterized in that the form of the duct (11) is substantially U-shaped. Insert heat exchanger (6) as claimed in any of the claims 1-4, characterized in that the heat exchanger is provided with an insert combustion chamber (9). Insert heat exchanger (6) as claimed in claim 5, characterized in that the combustion chamber (9) has a substantially circular cross section and connects onto an outlet duct (11) for combustion gases similarly to the duct (11). Insert heat exchanger (6) as claimed in claim 5 or 6, characterized in that the heat exchanger (6) with combustion chamber is arranged in a boiler (7) which is connected to a solar collector. Insert heat exchanger (6) as claimed in any of the claims 1-7, characterized in that a plate is arranged at a small distance beneath the heat exchanger (6) for generating a desired flow pattern of the second medium on the outside of the heat exchanger (6).

Inventors: LUIGJES TEUNIS, LUIGJES, TEUNIS
Applicants: LUIGJES ZONNE EN B V, LUIGJES ZONNE ENERGIE B.V.
Application year: 1994
Main classification: F28D1
IPC codes: F24H1, F28D7, F28D1